353 



The Alteration in Specific Gravity of Eucalyptus 

 Oils at Various Temperatures. 



As considerable differences occur in the specific gravities oi Eucalyptus oils .it 

 various temperatures, it was necessarj thai some standard bi i I lished win rebj 

 the several oils might be brought into uniformity. In Sydney the temperatun 

 during the summer months Ls usually high, and the ordinarj temperature in the 

 laboratory at thai period is often _•<> C. To reduce the oils to .1 standard tem- 

 perature by artificial means was out oi the question. It was decided, therefore, 

 to determine the increase or decrease for varying degrees of temperature within 

 ordinary working limits. A special pyknometer was ((instructed with a line 

 capillary, standardised at 15 C, and the specific gravity determined at the 

 temperatures given below, the figures being restricted to Eour places oi decimals. 

 The following results were obtained, experimentally, with a Eucalyptus oil rich 

 in cineol, and having a specific gravity 0-9156 at 15 C. :— 

 At in ('. specific gravity = 0-9190 



12° C. „ = 0-9179 



14° C. ,, = 0-9166 



15 C. ,, = 0-9156 



From these results it is seen that 0-00075 is practically the increase between 

 and 15' ('., and that the same figures represent the decrease between 15' and 

 C. Taking the standard specific gravity at 15 C, and calculating either upwards 

 or downwards, as the case maybe, the following figures are obtained, and it is seen 

 that they differ but little from those determined experimentally :— 



10 



26 



At 



10 



n c 



I2 C 



I3 C 

 M c 

 15° 

 i6 c 



i7 c 



IN 



C. specific gravity 

 C. 



c. 



c. 

 c. 

 c. 

 c. 

 c. 

 c. 



0-91935 



0-91860 



0-91785 



0-91710 



0-91635 



0-91560 



0-91485 



0-91410 



091335 



For all practical purposes, therefore, 0-00075 may be taken as the increase 

 or decrease, as the case maybe, for Eucalyptus oils within the range of ordinary 

 temperatures in the laboratory, and in this way the specific gravity at 15 C. 

 may be calculated for any Eucalyptus oil, providing the apparatus had been 

 standardised for 15 C. These figures have been repeatedlj checked during 

 this research, and have been found to agree very well for all those Eucalyptus 

 oils so tested. It is thus easy to determine the specific gravity oi a Eucalyptus 

 oil for 15 C. II, for instance, the specific gravity was found to be 0-9095 and 

 the temperature 21 C, then by adding 0-0045 we obtain 0-9] (.0 as the (directed 

 specific gravity for the particular sample at 15 C. 



Taking advantage of the colder weather in June, determinations were 

 made with two Eucalyptus oils belonging to differenl classes, in order to test the 

 accuracy of the differences recorded above. A specific gravity bottle holding 50 

 grams of water was employed for the purpose, and the temperature oi the oil 

 increased to the desired degree by artificial means. The crude oil oj I . Smithii 



